Colleges and high schools have such odd terminology. As if the alphabet soup of academic acronyms wasn't enough, there are all the strange terms - bursar, for example, yield and Jan Term. So when your child's counselor refers to him as a "rising senior," what on earth does that mean?
Once upon a time, a kid was a junior until June of his junior year. When the bell rang on the last day of school, he became a senior - even if the start of the next academic year was still two months away. Now, he's called a rising senior. (Clearly it's only a matter of time before preschoolers are called rising kindergartners.)
The term is primarily used at college prep high schools in the United States and when colleges discuss admissions season, as in "We offer overnight visits to rising seniors." Colleges rarely use the term to discuss their own students and in fact, the freshman/sophomore/junior/senior terminology is increasingly giving way to alternative descriptions based on how long a student has attended, as in "first year," "second year" and so on.